While safety from accidents and the safety systems of motor vehicles are being increasingly improved, up to now there have been virtually no practical approaches to increasing the road safety of pedestrians. In fact, pedestrians are particularly at risk in the case of accidents since, unlike the occupants of a motor vehicle, they are not protected by a crush zone or further active and passive safety systems which are possibly present.
In order to avoid injury to pedestrians in road traffic, the basic approach has already been followed of reducing the frequency of accidents by a computer installed in the vehicle signaling to the driver by means of a transponder system that there are pedestrians located in the vicinity of the vehicle.
DE 299 16 238 U1, which is incorporated by reference, discloses a method for integrating a transponder into a shoe which serves to prevent the shoe being stolen from a department store.
DE 100 28 219 A1, which is incorporated by reference, discloses a marking device for persons which can be attached, for example, to the person's clothing and which indicates the person's position by means of an invisible radiation signal or other signals (acoustic, optical). The marking device also senses data itself from its surroundings and can therefore alert the person to possible dangers. In order to supply power, this marking device can have means for converting movement energy and thermal energy into electrical power.
The disadvantage of contemporary transponders which are attached to persons is in particular the fact that these transponders are permanently switched on and therefore continuously consume electrical power. As a result, transponder systems which are operated by means of batteries regularly either require a change of battery or have to be completely replaced, which in turn entails increased costs. Transponder systems which have their own means for generating electrical power are an alternative to this. However, electrical power cannot be generated in every situation. For example, a generator which operates on the basis of temperature differences can, for example, generate electrical power only when a sufficiently large temperature gradient is also present. In addition it appears questionable whether the power required by these systems can actually be made available by such a generator. Passive transponder systems which are known per se and which convert the electromagnetic radiation emitted by a transmitter partially into electrical power for their own operation and then in turn irradiate back a portion of this electrical power as a radio wave are a further alternative. Although such systems are independent of batteries and microgenerators, their transmission power is so low that the transmitted signal typically only has a range of a few centimeters. This is generally not sufficient for safety applications in road traffic.